Grills including gas fired grills are popular and in wide use for cooking food. Such grills include a kettle which is frequently rectangular in shape and which has one or more burners mounted within it. Such burners are available in a number of configurations including bar burners, H-shaped burners and U-shaped burners. For example, U.S. Pat. No. 4,478,205 shows burners of the U-and H-shape types, U.S. Pat. Nos. 4,741,321 and 4,561,419 show bar burners and U.S. Pat. No. 4,705,020 shows a round burner.
Irrespective of the shape of the burner used within the grill, such grills often share a common problem. This problem is well illustrated by a rectangular kettle (the most common kettle shape) having within it a conventional bar burner. The cooking area is defined by a grill matrix made of wire or thin bars and placed atop the kettle and food is placed on this matrix for cooking.
Those areas of the cooking surface adjacent the corners of the kettle are located at a distance from the burner which is greater than those areas directly or nearly directly above the burner. The result is that those cooking areas nearer the corners of the kettle (and therefore farther from the burner) are at a much lower temperature than those areas near the center of the grill. For example, it is not unusual to experience differentials in temperature across the grill cooking surface which range from 130.degree. F. to over 320.degree. F. That is, the lowest temperature at the grill cooking surface may be 130.degree. F. to over 320.degree. F. lower than the highest temperature.
As a result, food distributed across the cooking surface cooks at a very uneven rate. This forces the grill user to serve food in sequential batches as cooking is completed or to periodically rearrange the food on the cooking surface so that all of the food is completely cooked at substantially the same time.
One factor which can aggravate and contribute to such temperature unevenness is that the burner itself "throws" or rejects heat unevenly with those portions of the burner nearer the inlet producing more heat than portions located farther from the inlet. This occurs because gas flowing from holes located more closely to the gas inlet is at a higher pressure and the flames produced thereby tend to be more robust. On the other hand, gas flowing from those holes located at the extremities of the burner, well away from the inlet, is at a lower pressure and the flames produced at such holes are "lazy" and reject less heat outward toward the adjacent cooking surface.
One known solution to the problem of uneven heat rejection involves the use of an interior baffle which prevents gas from flowing from the gas inlet port directly to those holes closest to such port. Instead, such gas is forced to flow along a serpentine path and the gas pressure at all of the holes tends to be more nearly equalized. As a consequence, the flames emanating from the holes tend to be more uniform in size and reject heat rather uniformly.
Another approach to the equalization of heat rejection is shown in U.S. Pat. No. 3,501,098 which shows a gas burner for a rotary dryer drum. The cylindrical burner shown therein is closed at each end and uses two horizontal rows of holes arranged one above the other and near the edge of an interior diametral baffle plate. Such holes face sideways along axes which are generally normal to the long axis of the burner. These holes, some of which face slightly upward and some of which face slightly downward, are nevertheless all "side facing" holes and are arranged in three zones on either side of the inlet. Such holes have diameters which increase with increases in distance of the zone from the centrally located fuel inlet. The holes within the zone nearest the inlet are spaced more closely together than are the holes in the other two zones and the flames emanating from all holes reject heat only in a sideways direction.
Another solution to the problem to non-uniform heat rejection is shown in U.S. Pat. No. 2,044,528. The Bunsen burner shown therein is designed to reject heat only in a upward direction. It has a progressively decreasing cross-sectional area (as viewed from the inlet toward the outer end) so that the burner gas holes are fed at a more nearly uniform gas pressure.
While such approaches reduce the problem of non-uniform heat rejection, they fail to adequately consider that certain areas of a cooking grill surface will nevertheless be at a substantially lower temperature even though heat is rejected rather uniformly from the burner itself. To state it another way, such heat is not sufficiently projected toward the extremities of the cooking surface such as the corners of a rectangular grill.
Another problem arising from burners of the "H," "U" and bar types illustrated in the aforementioned patents is that when such burners are mounted in a kettle, their top surfaces are generally horizontal and parallel to the cooking surface. Grease drippings and other types of debris inevitably fall to these top surfaces, often collecting in unsightly layers. In addition to the unsavory appearance presented by such debris, it often contains salt and can corrode and quickly destroy the burner unless regularly cleaned therefrom.
An improved burner which rejects heat in a manner to more nearly equalize the temperature across a grill cooking surface, which has improved efficiency, which tends to be self-cleaning of drippings and the like, which is devoid of baffles and otherwise easy to manufacture would be an important advance in the art.